[Matplotlib-users] Error with dates.DayLocator when specifying timezone?

[<PHobson@Geosyntec.com>]

Hey folks,

I'm plotting a simple rainfall record and when I tell the DayLocator to make sure to use 'US/Pacific' as it's time zone, it barfs on me. (US/Pacific is also set in my matplotlibrc file). When I don't specify the time zone, it doesn't barf, but the xticks are placed 8 hours off (presumably at the start of day GMT, right?). Am I not specifying the datetime.tzinfo object correctly?

The code and the traceback are below. The trace back mentions some EOF in a multi-line statement, but blames it on my fig.savefig(...) command.

Thanks for everything. This library is truly amazing. My mind is consistently blown as to what the developers have created.

Here's some code:
import numpy as np
import datetime as dt
import matplotlib.pyplot as pl
import matplotlib.dates as md

TZ = dt.tzinfo('US/Pacific')
dmin = dt.datetime(2009,12,22,0,0)
dmax = dt.datetime(2010,1,31,0,0)
delta = dt.timedelta(5/(24*60.))

dr = md.drange(dmin, dmax, delta)
y1 = np.zeros(len(dr)) + 1

fig = pl.figure(figsize=(7,4))
ax = fig.add_axes([0.10,0.13,0.85,0.82])

#~ --- this is where the error happens -------
#~ leave it as is for the point to be off 
#~ OR
#~ uncomment the next line to produce the error
days = md.DayLocator(interval=4)
# days = md.DayLocator(interval=4, tz=TZ)

# verify xtick locations
a = dt.datetime(2009,12,26,0,0,0)
b = 4.5

L1 = ax.plot(dr, y1, 'b-', lw=1, label='Hourly')
p1 = ax.plot(a,b,'g.', label='Point not @ start of day')

ax.legend(loc='upper right')
ax.xaxis.set_major_locator(days)
ax.xaxis.set_major_formatter(md.DateFormatter('%m/%d'))

fig.savefig('storm.png')
# -------------------------------------------------------

The traceback:
In [138]: run storm_tracker
ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (550, 0))

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (550, 0))

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (550, 0))

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (91, 0))

---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)

c:\stuff\utils\py\storm_tracker.py in <module>()
     59 ax.set_ylim([0,5])
     60 ax.set_xlim([dmin, dmax])
---> 61 fig.savefig('storm.png')
     62
     63

C:\Python26\lib\site-packages\matplotlib\figure.pyc in savefig(self, *args, **kwargs)
   1030                 patch.set_alpha(0.0)
   1031
-> 1032         self.canvas.print_figure(*args, **kwargs)
   1033
   1034         if transparent:

C:\Python26\lib\site-packages\matplotlib\backends\backend_qt4agg.pyc in print_figure(self, *args, **kwargs)
    142
    143     def print_figure(self, *args, **kwargs):
--> 144         FigureCanvasAgg.print_figure(self, *args, **kwargs)
    145         self.draw()
    146

C:\Python26\lib\site-packages\matplotlib\backend_bases.pyc in print_figure(self, filename, dpi, facecolor, edg
ecolor, orientation, format, **kwargs)
   1474                 orientation=orientation,
   1475                 bbox_inches_restore=_bbox_inches_restore,
-> 1476                 **kwargs)
   1477         finally:
   1478             if bbox_inches and restore_bbox:

C:\Python26\lib\site-packages\matplotlib\backends\backend_agg.pyc in print_png(self, filename_or_obj, *args, *
*kwargs)
    356
    357     def print_png(self, filename_or_obj, *args, **kwargs):
--> 358         FigureCanvasAgg.draw(self)
    359         renderer = self.get_renderer()
    360         original_dpi = renderer.dpi

C:\Python26\lib\site-packages\matplotlib\backends\backend_agg.pyc in draw(self)
    312
    313         self.renderer = self.get_renderer()
--> 314         self.figure.draw(self.renderer)
    315
    316     def get_renderer(self):

C:\Python26\lib\site-packages\matplotlib\artist.pyc in draw_wrapper(artist, renderer, *kl)
     44     def draw_wrapper(artist, renderer, *kl):
     45         before(artist, renderer)
---> 46         draw(artist, renderer, *kl)
     47         after(artist, renderer)
     48

C:\Python26\lib\site-packages\matplotlib\figure.pyc in draw(self, renderer)
    771
    772         # render the axes

--> 773         for a in self.axes: a.draw(renderer)
    774
    775         # render the figure text


C:\Python26\lib\site-packages\matplotlib\artist.pyc in draw_wrapper(artist, renderer, *kl)
     44     def draw_wrapper(artist, renderer, *kl):
     45         before(artist, renderer)
---> 46         draw(artist, renderer, *kl)
     47         after(artist, renderer)
     48

C:\Python26\lib\site-packages\matplotlib\axes.pyc in draw(self, renderer, inframe)
   1733
   1734         for zorder, i, a in dsu:
-> 1735             a.draw(renderer)
   1736
   1737         renderer.close_group('axes')

C:\Python26\lib\site-packages\matplotlib\artist.pyc in draw_wrapper(artist, renderer, *kl)
     44     def draw_wrapper(artist, renderer, *kl):
     45         before(artist, renderer)
---> 46         draw(artist, renderer, *kl)
     47         after(artist, renderer)
     48

C:\Python26\lib\site-packages\matplotlib\axis.pyc in draw(self, renderer, *args, **kwargs)
    734         renderer.open_group(__name__)
    735         interval = self.get_view_interval()
--> 736         for tick, loc, label in self.iter_ticks():
    737             if tick is None: continue
    738             if not mtransforms.interval_contains(interval, loc): continue

C:\Python26\lib\site-packages\matplotlib\axis.pyc in iter_ticks(self)
    675         Iterate through all of the major and minor ticks.
    676         """
--> 677         majorLocs = self.major.locator()
    678         majorTicks = self.get_major_ticks(len(majorLocs))
    679         self.major.formatter.set_locs(majorLocs)

C:\Python26\lib\site-packages\matplotlib\dates.pyc in __call__(self)
    476     def __call__(self):
    477         # if no data have been set, this will tank with a ValueError

--> 478         try: dmin, dmax = self.viewlim_to_dt()
    479         except ValueError: return []
    480

C:\Python26\lib\site-packages\matplotlib\dates.pyc in viewlim_to_dt(self)
    452     def viewlim_to_dt(self):
    453         vmin, vmax = self.axis.get_view_interval()
--> 454         return num2date(vmin, self.tz), num2date(vmax, self.tz)
    455
    456     def _get_unit(self):

C:\Python26\lib\site-packages\matplotlib\dates.pyc in num2date(x, tz)
    247     """
    248     if tz is None: tz = _get_rc_timezone()
--> 249     if not cbook.iterable(x): return _from_ordinalf(x, tz)
    250     else: return [_from_ordinalf(val, tz) for val in x]
    251

C:\Python26\lib\site-packages\matplotlib\dates.pyc in _from_ordinalf(x, tz)
    177     dt = datetime.datetime(
    178         dt.year, dt.month, dt.day, int(hour), int(minute), int(second),
--> 179         microsecond, tzinfo=UTC).astimezone(tz)
    180
    181     if microsecond>999990:  # compensate for rounding errors

NotImplementedError: a tzinfo subclass must implement utcoffset()
WARNING: Failure executing file: <storm_tracker.py>

Paul M. Hobson                  
Senior Staff Engineer
-- 
Geosyntec Consultants 
55 SW Yamhill St, Ste 200
Portland, OR 97204
Phone: 503.222.9518
www.geosyntec.com